The most important consideration is the clearance around the firebox, the distance immediately above, to the left and to the right of the firebox that must be made of noncombustible material If you have a prefab unit, the owner's manual should tell you what the clearances should be. If your unit is not prefab, the existing clearnace can serve as a guide. After all, if the fireplace has been safely used, then you know that the existing clearances are okay. Just stick to them and you'll be all right. If this is a fireplace that is PLANNED, and has not been built, you need to consult with the contractor who is building it for you to find out what the clearances should be. One overlooked clearance issue is the depth of the mantle -- the higher the mantle is from the top edge of the firebox, the deeper is can safely be. Otherwise it can get very hot because heat from the firebox rises. Of course, if the mantle is composed of marble or some other noncombustible material, you do not need to worry too much about its depth. Just remember that if it is very low (i.e., close to the upper edge of the firebox), it is likely to get pretty hot. I hope these considerations help you in your planning. If questions, post another message.

Sidney, Thanks so much for posting that picture as a creative solution. I think we should have the space to do something similar to what your posted, but would need to go down to displaying plates on one side with TV on the other. I certainly like the fireplace with built ins that you chose to do in your home as it achieves what I am trying to do as well - fireplace as the real focus, and TV hidden or down played. Do you find having your TV on a swing out arm convient? In real life do you have the TV swung out most of the time, and only hidden on the occasion? Do you have any issues with glare from windows on your set-up? Thanks again Sidney for your help. Hopefully, at some point I will have a nice fireplace with built-ins like you do. Carol

So it sounds like your builder or architect needs to do a bit of detailing so as to try to offset the framing to receive the cabinets and shelf and mantel.... your original source image shows the fire place on an exterior wall and is gas burning which is normally bigger then some gas appliances. so the sketch on the right is what I can make out based on pictures. Good luck !! If you ever need a designer in CA give MSDG a try...

Adding a wood mantle is a great idea and in regards to bookcases, maybe consider cabinets and open shelving to match mantle. With the other bookcases in room, there is a bit of bookcase overload If you do want something like the look below, make sure the bookcases reach the ceiling and have a trim for a more finished look. Really important as well is how you accessorize shelves and mantle and there is lots of on line help When you reference help with layout, hard to suggest - is there any other location for sectional? In regards to lighting, add lamps to side tables, a floor lamp located where it’s needed and if you don’t need the ceiling fan/light, replace with something that provides good lighting and also place on a dimmer. You can get a lot of ideas by searching Houzz and Pinterest for inspiration, as it is hard to know how much you want to change.